The invention relates to an apparatus (according to the preamble to claim 1) and to a method (according to the preamble to claim 17) for the production of cement clinker from cement raw material.
An apparatus and a method of the aforesaid type are known for example from EP 0 764 614 B1. In this known construction the gasification reactor is connected by its lower end directly to an exhaust gas pipe which leads to or contains the calcination zone, so that on the one hand the product gas generated in the reactor is introduced as combustion gas or fuel into the calcination zone and on the other hand the incompletely gasified residues of the waste-derived fuels gasified or degasified in the reactor are evacuated via the exhaust gas pipe into the kiln inlet. In the gasification reactor the lumpy waste-derived fuels, particularly scrap tyres, are gasified with tertiary air from the clinker cooler.
The object of the invention is make further improvements to apparatus according to the preamble to claim 1 as well as a method according to the preamble to claim 17 so that, by comparison with the known construction described above, above all the speeds of conversion of the lumpy waste-derived fuels or secondary fuels, i.e. the progress of gasification of these waste-derived fuels, can be markedly increased with the most favourable dimensions possible of the reactor and the product gas which is generated can be used as fuel at various points in the cement production process.
This object is achieved according to the invention on the one handxe2x80x94in relation to the apparatusxe2x80x94by the characterising features of claim 1 and on the other handxe2x80x94in relation to the method of manufacturexe2x80x94by the characterising portion of claim 17.
Advantageous embodiments and further developments of the invention are the subject matter of the subordinate claims.
A first essential idea underlying the present invention is that in the gasification reactor in the region above a solids bed made up of the waste-derived fuels there is constructed a reagent introduction zone which extends over the reactor cross-section and into which reagent introduction connections which are regularly distributed over the circumference of the reactor open in such a way that in the region of the introduction zone the reagent can be introduced with a high pulsation to create a pre-selected flow form. Due to the gasification agent or reagent introduced in this way for instance in the form of branch streams with a high inlet pulse, in the region of the said introduction zone above the solids bed made up of the waste-derived fuels a favourable flow form (or flow pattern) is produced in such a way that the gasification reaction proceeds in a manner largely determined by the surface, which due to optimum setting of the said flow form (with the formation of a corresponding flow and temperature field) leads to a particularly high gasification efficiency. Thus particularly high conversion speeds of the lumpy waste-derived fuels can be brought about for the generation of the product gas to be exploited as combustible gas or fuel. This optimum progress of the gasification in the gasification reactor also brings with it the further advantage that the structural dimensions of the reactor used here can be kept relatively small.
In this construction according to the invention, furthermore, in a particularly advantageous manner the fuel gas pipe has associated with it at least one gas conveying arrangement for the supply of the fuel gas (product gas) generated in the gasification reactor to at least one combustion zone. In this connection it should already be pointed out that this apparatus according to the invention (and also the method according to the invention, which will be dealt with later) can generally be designed so that the calcination zonexe2x80x94as is known per sexe2x80x94can either be disposed as a separately constructed arrangement (calciner) in the region between the preheating zone or preheater and the kiln inlet or can be constructed in a first longitudinal section of the kiln designed as a rotary kiln, so that in the first case (separately constructed calcination arrangement) the calcination zone also simultaneously forms a further combustion zone and is supplied with fuel, via a separate fuel pipe or fuel gas branch pipe, whilst the sintering combustion zone contained in the kiln is supplied with fuel separately via its burner or main burner; by contrast, the apparatus contains only one single combustion zone, namely the sintering combustion zone referred to above, if the calcination zone is constructed in the first longitudinal section of the kiln (rotary kiln). Thus the optimally generated fuel gas can be used as fuel in various combustion zones (combustion sites).
According to an advantageous embodiment of the apparatus according to the invention, substantially all of the reagent introduction pipes open into the reagent introduction zone in the same horizontal plane, whereby for the formation of the predetermined flow form in the introduction zone the central axis of each introduction connection deviates downwards at an acute angle from a (radial) reference line directed to the centre of the reactor cross-section and/or from the said horizontal plane. Thus in the reagent introduction zone, above the solids bed made up of waste-derived fuels, a desired rotational flow is imposed upon the introduced reagent which has a positive influence on the material or heat transfer between the reagent and the waste-derived fuels.
In this construction according to the invention it is also advantageous if the horizontal plane in the gasification reactor defined by the orifices of the reagent introduction pipes is a predetermined clear vertical distance from the upper face of the solids bed, whereby it is advantageous ifxe2x80x94for example as a function of the respective composition or type of the waste-derived fuels) this vertical distance can be adjusted or regulated within advantageous ranges.
According to a further advantageous embodiment of the invention it is advantageous if fans and/or injectors operated by means of compressed air or steam are provided as gas conveying arrangements in the gas supply pipe to the gasification reactor and in the fuel gas pipe. In this way on the one hand the flow pulse with which the reagent is introduced, preferably blown in, into the gasification reactor and on the other hand the supply of the generated fuel gas to at least one combustion site (in the calcination zone and/or the sintering combustion zone) can be optimally controlled.
The method according to the invention for the production of cement clinker is characterised above all in that in the gasification reactor above a solids bed made up of the waste-derived fuels the hot gaseous reagent is introduced at a plurality of supply sites distributed over the circumference of the reactor, forming a reagent introduction zone which extends over the reactor cross-section with a high pulsation and with a pre-selected flow form (flow pattern) and the fuel gas generated in the gasification reactor is supplied as fuel to thexe2x80x94at least onexe2x80x94combustion zone.
In this method according to the invention it is also particularly advantageous if the fuel gas generation in the gasification reactor is carried out under reducing conditions and the reactor is operated with an underpressure of at least 0.1 mbar. This prevents generated fuel gas from escaping in an undesirably manner out of the gasification reactorxe2x80x94apart from through the fuel gas pipe/pipes.